I think it's simpler than that. Canva's primary competitor is Adobe, and Adobe's remaining advantage is with creative professionals. That's Adobe's core market and their core revenue stream.
It's a classic "commoditize your complements" play. Canva remains profitable without charging for Affinity, but Adobe can't stay profitable if they stop charging for Photoshop/Illustrator.
The business justification works without imputing any more sinister motives than that.
I mean, 9/10ths of the dark-pattern distrustworthy bullshit businesses pull is not required to attain or maintain "profitability," it's just squeezing every dime of revenue from their customers.
I would frankly rather pay for software then be left wondering if I can trust free commercial software.
Would be really nice if we had more of the "just pay" options. As it is the "just pay" options mostly also can't be trusted any more than the free(-mium) options, and both will try their best to "squeeze every dime of revenue".
It's a classic "commoditize your complements" play. Canva remains profitable without charging for Affinity, but Adobe can't stay profitable if they stop charging for Photoshop/Illustrator.
The business justification works without imputing any more sinister motives than that.